In a typical muffler system, a portion of the sound energy delivered to the muffler is reflected back towards the source, a second portion is dissipated through a baffling arrangement in the muffler, while the remainder of the sound energy is transmitted to the atmosphere through the shell or body of the muffler and through the outlet. In any silencing system it is desired to provide maximum sound attenuation with minimum pressure restriction.
The conventional muffler comprises a series of sections or elements, such as an inlet section, an outlet section, and perhaps one or more intermediate sections. One commonly used section is what is referred to as a plug section. In a plug section, the exhaust gas enters the section through an inlet pipe and the inner end of the pipe is closed or plugged, causing the gas to flow outwardly through perforations in the inlet pipe into an outer chamber. This arrangement is known to be effective in attenuating sound energy.
More recently, various modifications of the basic plug section have been used in an attempt to increase the effectiveness of the sound energy attenuation.